Atmospheric Chemistry Experiment (ACE) measurements of elevated Southern Hemisphere upper tropospheric CO, C2H6, HCN, and C2H2 mixing ratios from biomass burning emissions and long-range transport -: art. no. L20803

Infrared Fourier transform spectra recorded at 0.02 cm(-1) resolution by the Atmospheric Chemistry Experiment (ACE) show elevated levels of the relatively long-lived biomass burning products CO, C2H6, HCN, and C2H2 in the upper troposphere and lower stratosphere at 15 degrees S-45 degrees S latitude from 30 September to 3 November 2004. Mixing ratios up to 260 ppbv (10(-9) per unit volume) for CO, 1470 pptv (10(-12) per unit volume) for HCN, and 1.67 ppbv for C2H6 are observed in the upper troposphere and their variations are highly correlated reflecting their similar lifetimes and emission origin. Back trajectory calculations and maps of fire distributions for the time period indicate the elevated levels likely originated from regions of tropical fire emissions in South America or Africa with cases identified with elevated emissions reaching close to the lower stratosphere.